This study was undertaken to investigate ocular asymmetries in binocular vision using several dichoptic and binocular viewing paradigms. The literature on eye dominance was reviewed and it revealed that little emphasis both theoretically and experimentally had been placed on binocular viewing situations. The nature of the eye dominance tests and the dichotomous classification of the results suggested that one eye's image was competing against the other. The relationship between the different eye-dominance tests was not clear. A new approach to the study of ocular dominance has been developed in this thesis with specific attention to binocular vision and viewing situations. The term eye dominance has been replaced by the term ocular asymmetries to describe the results and measures derived from these procedures and the nature of the binocular visual approach. The experimental work is divided into three sections. Section one, is concerned with a binocular rivalry procedure using real images and afterimages. Section two, involves a stereoscopic viewing procedure and depth discrimination task with selective attenuation of the stereo-displays. Section three, investigates the interocular transfer of the spatial frequency shift. Measures of ocular asymmetry were derived, from all three procedures and the three sets of scores were positively related. This measure gives both the direction and the degree of the ocular asymmetry. The results indicate that ocular asymmetries are a valid feature of binocular vision. The new measure derived from the depth discrimination experiment provides a quantitative and consistent measure of ocular asymmetry. Special attention has been directed at the involvement of eye movements in all three paradigms and as the underlying factor in the asymmetry results. On the basis of the findings it was suggested that the asymmetry may reside in the binocular system controlling eye movements or reflect an asymmetry in processing speeds of the images from the two eyes arriving at the binocular site. The ocular asymmetry measures do not necessarily indicate eye movements are asymmetrical. It is recommended that ocular asymmetry is a variable to be studied in other investigations of binocular vision and binocular interactions.

The interocular transfer of simultaneously presented visual discriminations was examined in the pigeon (Columba livia) in several experimental situations. When trained monocularly on a jumping stand, there was no evidence of transfer to the other eye-hemisphere system of either pattern or colour discriminations using retraining and reversal learning measures as well as testing. This failure was not due to any obscuring of transfer consequent upon switching the occluder from one eye to the other, nor was there any suggestion of even a small amount of transfer of information from the trained eye to the untrained eye with extensive overtraining and decoupling trials. Binocular training on the jumping stand also revealed that some of the pigeons were learning a discrimination with only one eye in spite of the opportunity to learn with both eyes. When trained in a key pecking task, pigeons demonstrate perfect transfer. Testing revealed that this discrepancy in results is not due to the number of trials given in the two situations, to separation of the stimuli over a greater distance or by a partition, nor to the distance at which the pigeon makes a decision about which stimulus to approach. When the function of the retinal locus of the stimuli was examined, evidence was found in the literature and in my observations that the pigeons were using a different part of the retina when scanning the stimulus display in a key pecking task than on the jumping stand, even though the stimuli in the two situations were located in the same position relative to the bird's head. Specifically, in the key pecking tasks the red area of the retina, which serves the lower binocular portion of the retina, is used. On the jumping stand this area is not used to scan the stimuli. It was then possible to demonstrate a failure of transfer in a key pecking task and successful transfer on the jumping stand by simply manipulating whether the red area was used in scanning the stimuli. The results are discussed in terms of a consequence of binocular convergence from the red area, and when there is a failure of transfer, when the red area is not used, or prevented from being used, the stimuli fall within the monocular field where there is no necessity of later convergence from the two inputs. Active inhibition mechanisms also might serve to lateralize input to one hemisphere.

William Eric Leifur Grimson. / Based on the author's thesis (Ph.D.--Massachusetts Institute of Technology) Includes indexes. / Bibliography: p. [247]-267.